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<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <!-- 比如用户输入的是10， 则计算 1~10 之间的累加和 -->

    <script>
        let num = 0;
        for (let i = 1; i <= 10; i++) {
            num += i;
        }
        document.write(`${num}`)
    </script>

</body>

</html>